WALL_FACTOR_FD

This function computes a wall-property correction factor for pressure-drop or friction-factor correlations. It modifies constant-property friction predictions based on the ratio of bulk to wall viscosity (or Prandtl number analog).

The correction is expressed as:

\frac{f_d}{f_{d,cp}} = \left(\frac{\mu}{\mu_{wall}}\right)^n

The exponent n is selected from empirical values based on flow regime (laminar or turbulent) and phase model (liquid or gas).

Excel Usage

=WALL_FACTOR_FD(mu, mu_wall, turbulent, liquid)
  • mu (float, required): Viscosity of fluid away from the wall (Pa*s).
  • mu_wall (float, required): Viscosity of the fluid at the wall (Pa*s).
  • turbulent (bool, optional, default: true): Whether turbulent coefficients are used.
  • liquid (bool, optional, default: false): Whether liquid-phase coefficients are used.

Returns (float): Wall correction factor for friction factor or pressure drop (-).

Example 1: Turbulent liquid pressure drop factor

Inputs:

mu mu_wall turbulent liquid
0.0008 0.0003 true true

Excel formula:

=WALL_FACTOR_FD(0.0008, 0.0003, TRUE, TRUE)

Expected output:

0.782542

Example 2: Laminar liquid pressure drop factor

Inputs:

mu mu_wall turbulent liquid
0.0008 0.0003 false true

Excel formula:

=WALL_FACTOR_FD(0.0008, 0.0003, FALSE, TRUE)

Expected output:

0.566159

Example 3: Turbulent gas pressure drop factor

Inputs:

mu mu_wall turbulent liquid
0.000015 0.000013 true false

Excel formula:

=WALL_FACTOR_FD(0.000015, 0.000013, TRUE, FALSE)

Expected output:

1.01441

Example 4: Laminar gas pressure drop factor

Inputs:

mu mu_wall turbulent liquid
0.000015 0.000013 false false

Excel formula:

=WALL_FACTOR_FD(0.000015, 0.000013, FALSE, FALSE)

Expected output:

0.866667

Python Code

Show Code 
from ht.core import wall_factor_fd as ht_wall_factor_fd

def wall_factor_fd(mu, mu_wall, turbulent=True, liquid=False):
    """
    Compute a wall correction factor for frictional pressure loss.

    See: https://ht.readthedocs.io/en/latest/ht.core.html

    This example function is provided as-is without any representation of accuracy.

    Args:
        mu (float): Viscosity of fluid away from the wall (Pa*s).
        mu_wall (float): Viscosity of the fluid at the wall (Pa*s).
        turbulent (bool, optional): Whether turbulent coefficients are used. Default is True.
        liquid (bool, optional): Whether liquid-phase coefficients are used. Default is False.

    Returns:
        float: Wall correction factor for friction factor or pressure drop (-).
    """
    try:
        return ht_wall_factor_fd(mu, mu_wall, turbulent=turbulent, liquid=liquid)
    except Exception as e:
        return f"Error: {str(e)}"

Online Calculator

Viscosity of fluid away from the wall (Pa*s).
Viscosity of the fluid at the wall (Pa*s).
Whether turbulent coefficients are used.
Whether liquid-phase coefficients are used.